Such an exhaust muffler is known from DE 197 20 410 A1. The exhaust gases released by an internal combustion engine flow in this prior-art exhaust muffler into the first chamber in the muffler housing via an inlet pipe or a first inlet opening area provided thereon and into the second chamber in the muffler housing via a second inlet opening area provided at one end of the inlet pipe. A connection pipe providing a connection opening between the second chamber and the first chamber is closed by an exhaust valve arrangement at its end area located in the first chamber. The exhaust valve arrangement is prestressed by a spring in the direction of a closed position, in which the connection pipe and hence the connection opening provided thereby between the second chamber and the first chamber is closed. At a sufficient speed of the internal combustion engine and hence with increased exhaust gas stream, or increasing exhaust gas pressure in the inlet pipe, the exhaust gas pressure in the second chamber and hence also in the connection pipe is increased by exhaust gases entering the second chamber in the second inlet opening area until the exhaust valve arrangement opens against the closing force provided by the spring.
An exhaust valve arrangement, which comprises a valve element pivotable in an exhaust pipe between a closed position and an open position, is known from DE 10 2004 040 631 B3. The valve element is prestressed in the direction of the closed position by a leg spring acting on the valve element. The valve element can be pivoted by the exhaust gas pressure against the prestressing force generated by the leg spring in the direction of its open position.
U.S. Pat. No. 7,434,570 B2 discloses a valve element of an exhaust gas arrangement, which valve element is pivotable in an exhaust pipe between a closed position and an open position. The valve element is coupled with a lever for being pivoted together. A spring acting on the valve element in the direction of the closed position acts on the lever. The effective lever arm, with which the spring force acts on the lever, decreases during the pivoting of the valve element from the closed position to the open position and the accompanying pivoting of the lever, so that the action of the spring, which is increasingly stressed during the pivoting of the valve element to its open position, increases degressively.